1. Field of the Invention
The present invention relates to a system disconnection detection (SDDC) circuit for a distributed location power source (DLPS) connected to a power system through a line, so that when system disconnection occurs, the system disconnection can be detected in order to isolate or stop the operation of the distributed location power source connected to the line that has disconnected from the power system.
2. Background Information
A distributed location power source is basically made up of a generating element and an inverter for converting the output from the generating element into an AC output. For example, with this type of distributed location power source provided in individual housing facilities, then a device such as a solar cell could be used as the generating element.
FIG. 15 shows a conventional type of system disconnection detection circuit for a distributed location power source.
In FIG. 15, a distributed location power source (DLPS) 140 comprises a DC power source 1, an inverter 2, a circuit breaker 4 and a receiver 3. The DC power source 1, acting as a generating element, is connected to the DC input terminal of the inverter 2. A load 5 is connected to the AC output terminal of the inverter 2 through the circuit breaker 4 and a line 9. The circuit breaker 4 if the distributed location power source 140, and a circuit breaker 7 of a power system 6 are connected together by the line 9. A signal notifying the opening of the circuit breaker 7 is fed to the receiver 3 via a dedicated signal line 8.
With this arrangement, when system disconnection occurs, that is, the circuit breaker 7 of the power system 6 opens, voltage is applied to the circuit breaker 7 from the distributed location power source 140 via the line 9. In other words, a reverse voltage condition arises, posing a danger to control of the circuit breaker 7 and causing problems with power system security. To avoid this, a signal informing of the opening of the circuit breaker 7 is transmitted to the receiver 3 via the dedicated signal line 8, and the circuit breaker 4 is opened by means of the receiver 3, thereby isolating the distributed location power source 140. That is to say, either the line 9 is disconnected or operation of the inverter 2 is stopped.
In this type of conventional system disconnection detection circuit, if the signal from the point of system disconnection informing of the system disconnection is not received, then system disconnection cannot be detected. Usually, the distance between the distributed location power source 140 and the power system 6 is great. Accordingly, the dedicated signal line 8 for the system disconnection informing signal must also be very long, and furthermore, since facilities for setting up the signal line are also necessary, the conventional system disconnection detection circuit is extremely expensive.